Microscopy in gemmology is used to determine gemstones and for quality control; these devices are used to visualize internal features, for example. In gemmology, all optically visible irregularities inside gemstones are understood as inclusions – such as material foreign bodies (minerals, liquids, gases), cracks, color zoning or twin lamellae. They are often not visible to the naked eye, unless a microscope is used. The type and shape of the inclusions often also allow conclusions to be drawn about which gemstones they are and from which outlets they originate. How is that possible? It has been proven that the origin and method of formation of gemstones can manifest themselves in characteristic inclusions. That needs to be investigated.
Depending on the device, gemstone microscopes can be used horizontally as well as vertically. In addition to the usual microscope components, gemstone microscopes have stone and cuvette holders and polarisation filters. All A.KRÜSS microscopes for gemmology are Stereo microscopes.
Stereo microscope function
The Stereo microscope is a special light microscope in which a separate beam path is provided for both eyes. Both eyes therefore see the stone under examination from a slightly different angle, so that a stereo effect occurs. The human brain combines the two images into a single image with some depth. This creates an almost spatial impression, which is the reason for the name stereo (two-channel) microscope.
The most common method and illumination of stereomicroscopy: bright-field microscopy is one of the most important ways of examining gemstones. It can be used to recognize most of the internal features of a gemstone. In bright-field microscopy, the stone is illuminated from below and thus examined under a microscope in this transmitted light. The example shows zircon grains with stress cracks in ruby, Place of orgin: Sri Lanka.
Function examine with immersion liquid
Gemstones are embedded in different immersion liquids to improve microscopy. This makes it possible to observe the stone from different angles.
Horizontal positioning of the microscope is a methodical advantage for these investigations. Disturbing reflections of the surface or the stone facets disappear due to the liquid; the inclusions then appear to float in the stone or the liquid. The exampleshows a composite imitation of wo stones, a garnet-glass doublet. You can find further practical tips in the Applications: Observe inclusions & determine places of orgin.
Do you want to read more?
If you are looking for more expert information, please order the white paper “Gemstone Microscopy”. The following examination methods are described in the specialist publication:
- Gemstone interiors as seen through the Stereo microscope
- Function and illumination for bright-field microscopy
- Function and illumination with Polarisation device
- Function and illumination with Dark-field microscopy
- Function and illumination with incident light device for Dark-field microscopy
- Examining under a microscope with immersion liquid
- Rubies are they natural or lab-created?
- View characteristic inclusions of aquamarine
- Finding the emerald
- Investigating a ruby with bright field illumination
- View rutile needles (TiO₂) in natural sapphire
The whitepaper was produced in collaboration with Prof. Dr. Jochen Schlueter wrote. a qualified mineralogist in charge of the permanent collection on display at the Mineralogical Museum in Hamburg.
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